Bahrain Mirror (Reuters): Iraq denied on Sunday that its security forces had used live ammunition against protesters who broke into Baghdad's heavily-fortified Green Zone this week.

Sources from four hospitals and Baghdad's central morgue said four protesters had been killed and 90 injured by gunshot wounds on Friday in the zone, which is in the centre of the capital and is home to parliament, government offices and embassies.

But Saad al-Hadithi, spokesman for Prime Minister Haider al-Abadi, said an initial investigation showed there had been only two deaths and no direct gunfire.

"There is no evidence that the two deaths were caused by direct gunfire on the protesters, and there are no other cases," he said in a speech broadcast on state television.

Hadithi suggested the demonstrations had been infiltrated by gunmen and said three protesters had been detained for interrogation but later released.

Friday's demonstrations included supporters of powerful Shi'ite Muslim cleric Moqtada al-Sadr as well as people from other groups upset with the government's failure to approve anti-corruption reforms and maintain security in the city.

The security forces used rubber bullets, water cannon and tear gas to disperse the thousands of demonstrators. Witnesses said they had shot into the air but later opened fire directly on civilians.

A politician from Sadr's movement condemned the use of live ammunition as "oppressive". Unverified photos posted online showed dozens of bullet casings.

Civilians have breached the Green Zone's perimeter twice in three weeks, raising questions about the government's ability to secure the capital, which has also seen a spike in bombings this month claimed by Islamic State.

Abadi has condemned the incursions and warned against chaos and strife as government forces seek to keep up momentum in their fight to drive the jihadists out of large swathes of northern and western Iraq that they seized in 2014.

Iraq's military said on Sunday it was preparing to launch an offensive to retake the Islamic State stronghold of Falluja and told residents to get ready to leave before fighting started.